Simon, not to sure which 50l trolleys you consider a rip off, but mine is anything but that.
Mine is the aquatech one, two 25l containers, very efficient.
I know of one guy who has a full van mount system, most of the time he and his wife use their Omnitrolleys on domestic work.
They open the van, lift out the trolleys (never full to the brim, they top them up to whatever level they need from the main tank) and off they go.
Very quick, very efficient.
There are other times when they work directly from their van (a Citroen Relay). All depends on circumstances.
The learning curve is steep, but once you have cracked it, and adapted it to fit in with your round it is just so efficient.
Spotting will occur now and then, and sometimes there are windows that just won't be able to be cleaned well with WFP, but you learn those as you go around your round.
Mostly, for UPVC, Georgian, leaded and so on, WFP is king.
For windows with oxidized frames its a different matter
Be adaptable, keep learning!
Regards
Ian